Diffusible Dye Forming Compounds
The use of diffusible dyes in photographic image transfer systems is well known, as is the formation of diffusible dyes from nondiffusing dye forming compounds. Whitmore and Mader, in British Patent Specification Nos. 840,731 and 904,364 and in U.S. Pat. No. 3,227,550, discuss the use of such compound is in certain image transfer photographic systems. Their inventions utilized preferred diffusible dye forming compounds which may be described as couplers of the general structure EQU R--Cp--R'
where Cp is a coupler residue forming a dye with a p-phenylenediamine or other developing agent, R is a removable substituent in the coupling position such as a ballast group rendering the coupler nondiffusing or a removable preformed dye molecule, and R' is a ballast group or a solubilizing group in a noncoupling position of the coupler residue. Either R or R' or both may contain solubilizing groups rendering the dye formed or split off during or after development diffusible in the photographic element wetted with processing solutions such as alkaline development solutions.
Dappen and Smith in U.S. Pat. No. 3,743,504 disclose the use of immobile diffusible-dye-forming couplers and immobile diffusible-dye-releasing couplers in a color diffusion transfer system.
Minagawa, Arai, and Ueda in U.S. Pat. No. 4,141,730 disclose the use of immobile colored coupling compounds which release diffusible dye during color development. These compounds are used to advantage in masking applications.
Sakanoue, Hirano, Adachi, Minami, and Kanagawa in German Often. No. 3,324,533 A1, Booms and Holstead in U.S. Pat. No. 4,420,556, and Arakawa and Watanabe in European Patent Specification 115,303 B1 disclose the use of diffusible dye forming couplers to provide photographic materials with improved graininess.
Figueras and Stern disclose in U.S. Pat. No. 3,734,726 the use of substantially colorless m-sulfonamidoaniline and m-sulfonamidophenol compounds that react with oxidized color development agents to release a coupler moiety that couples with oxidized color developing agent to produce diffusible dye in color diffusion transfer elements and processes. Fleckenstein discloses in U.S. Pat. No. 3,928,312 and Fleckenstein and Figueras disclose in German Offen. No. 2,242,762, in U.S. Pat. No. 4,076,529 the use of p-sulfonamidoaniline, p-sulfonamidophenol, p-sulfonamidonaphthol, and related compounds which react with oxidized color development agents to release diffusible dyes in color diffusion transfer elements and processes.
Bloom and Stephens in U.S. Pat. Nos. 3,443,939 and 3,498,785, Bloom and Rogers in U.S. Pat. No. 3,443,940, and Bloom in U.S. Pat. No. 3,751,406 disclose the use of m-amidophenols, m-amidoanilines, and related compounds that release dyes or dye precursors upon reaction with oxidized color developer m color diffusion transfer units and processes.